Automatic closures are known; two are disclosed in U.S. Pat. Nos. 3,425,578 and 3,561,591. The closures disclosed therein have a plurality of moveable parts and are expensive to manufacture. As a further disadvantage those closures are prone to stick in the open position when granular material is dispensed, due to the type of motion involved as the closure attempts to automatically close. Moreover, those closures do not open with a measured level of difficulty. This makes them easily openable by children and unsuitable for containers of caustic or poisonous material.
Many "child-proof" containers for caustic or poisonous material are known but none incorporate self-closing features. Such containers may be child-proof in the sense that the containers are difficult to open; however, once the containers are open, they remain so and nothing denies children access to their contents.